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Question for the day. [message #330019] Thu, 15 March 2018 12:44 Go to next message
Ken Burton is currently offline  Ken Burton   United States
Messages: 10030
Registered: January 2004
Location: Hebron, Indiana
Karma: 10
Senior Member
1978 GMC

On the one I am recovering after 19 years of inactivity, I have no brakes. The master cylinder REAR reservoir is almost FULL and the FRONT reservoir is bone DRY. There is a leak somewhere. My question is on the earlier GMCs the rear most reservoir if for the front brakes and the front reservoir is for the rear brakes.

I remember something about the 1978 reservoir being was different (maybe reversed) from previous years.

Is the front master cylinder reservoir for the rear brakes on a 1978 GMC?


Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
Re: [GMCnet] Question for the day. [message #330020 is a reply to message #330019] Thu, 15 March 2018 13:49 Go to previous messageGo to next message
johnd01 is currently offline  johnd01   United States
Messages: 354
Registered: July 2017
Location: Sacrameot
Karma: -1
Senior Member
If you think the problem is the front calipers, start there, it is much
easier to check them than to check the 4 cylinders in the back.

On Thu, Mar 15, 2018 at 10:44 AM, Ken Burton wrote:

> 1978 GMC
>
> On the one I am recovering after 19 years of inactivity, I have no
> brakes. The master cylinder REAR reservoir is almost FULL and the FRONT
> reservoir
> is bone DRY. There is a leak somewhere. My question is on the earlier
> GMCs the rear most reservoir if for the front brakes and the front reservoir
> is for the rear brakes.
>
> I remember something about the 1978 reservoir being was different (maybe
> reversed) from previous years.
>
> Is the front master cylinder reservoir for the rear brakes on a 1978 GMC?
> --
> Ken Burton - N9KB
> 76 Palm Beach
> Hebron, Indiana
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>



--

*John Phillips*
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Johnd01 John Phillips Avion A2600 TZE064V101164 Rancho Cordova, CA (Sacramento)
Re: [GMCnet] Question for the day. [message #330021 is a reply to message #330020] Thu, 15 March 2018 14:53 Go to previous messageGo to next message
James Hupy is currently offline  James Hupy   United States
Messages: 6806
Registered: May 2010
Karma: -62
Senior Member
Bob, UNLESS SOMEONE HAS CHANGED IT, the forward most reservoir is for the
rear drum brakes. If it is empty, you have a leak. Most likely the wheel
cylinders, but it could be a line as well.
Jim Hupy
Salem, Or
78 GMC ROYALE 403

On Mar 15, 2018 11:50 AM, "John Phillips" wrote:

If you think the problem is the front calipers, start there, it is much
easier to check them than to check the 4 cylinders in the back.

On Thu, Mar 15, 2018 at 10:44 AM, Ken Burton wrote:

> 1978 GMC
>
> On the one I am recovering after 19 years of inactivity, I have no
> brakes. The master cylinder REAR reservoir is almost FULL and the FRONT
> reservoir
> is bone DRY. There is a leak somewhere. My question is on the earlier
> GMCs the rear most reservoir if for the front brakes and the front
reservoir
> is for the rear brakes.
>
> I remember something about the 1978 reservoir being was different (maybe
> reversed) from previous years.
>
> Is the front master cylinder reservoir for the rear brakes on a 1978 GMC?
> --
> Ken Burton - N9KB
> 76 Palm Beach
> Hebron, Indiana
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>



--

*John Phillips*
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Re: [GMCnet] Question for the day. [message #330023 is a reply to message #330020] Thu, 15 March 2018 16:07 Go to previous messageGo to next message
Ken Burton is currently offline  Ken Burton   United States
Messages: 10030
Registered: January 2004
Location: Hebron, Indiana
Karma: 10
Senior Member
You have confirmed exactly what I thought. It was just that I remembered that there was something different on a 1978. I sucked dry the rear reservoir and filled both before I left last night. I have not bleed the fronts yet. I will start looking at lines and wheel cylinders for the rears. I'm guessing that I will find a rusted through line somewhere.

Thanks Jim.


Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
Re: [GMCnet] Question for the day. [message #330033 is a reply to message #330023] Thu, 15 March 2018 19:11 Go to previous messageGo to next message
tphipps is currently offline  tphipps   United States
Messages: 3005
Registered: August 2004
Location: Spanish Fort, AL
Karma: 9
Senior Member
Ken, Think about the combination valve. My steel one rusted the sliding valve in one position. This resulted in one empty compartment in the MC because the seals eventually failed.
If you do not have the brass combination valve, get one and change it out. You will be much happier.
Tom, sent from Perry GA FMCA rally.
See you in Tucson


2012 Phoenix Cruiser model 2552 KA4CSG
Re: [GMCnet] Question for the day. [message #330036 is a reply to message #330033] Thu, 15 March 2018 19:30 Go to previous messageGo to next message
Ken Burton is currently offline  Ken Burton   United States
Messages: 10030
Registered: January 2004
Location: Hebron, Indiana
Karma: 10
Senior Member
I'll keep that in mind. I do have a solid brake light on which I assume was caused by me stepping on the brake with no fluid in one of the two reservoirs. I'm hoping that light resets when I get both sides up to pressure.

I will look around the valve for leaks.

I did not make it out there today. I'm busy with a collapsed driveway culvert. I'll probably look for the leak tomorrow.

Thanks Tom


Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
Re: [GMCnet] Question for the day. [message #330037 is a reply to message #330036] Thu, 15 March 2018 19:42 Go to previous message
James Hupy is currently offline  James Hupy   United States
Messages: 6806
Registered: May 2010
Karma: -62
Senior Member
Ken, the brake warning light is a sign that your distribution valve is
functional. If it were full of crud, the valve would not move, and the
light would probaby not come on. You are right about when you bleed the
brakes, the light should go out.
Jim Hupy

On Mar 15, 2018 5:31 PM, "Ken Burton" wrote:

> I'll keep that in mind. I do have a solid brake light on which I assume
> was caused by me stepping on the brake with no fluid in one of the two
> reservoirs. I'm hoping that light resets when I get both sides up to
> pressure.
>
> I will look around the valve for leaks.
>
> I did not make it out there today. I'm busy with a collapsed driveway
> culvert. I'll probably look for the leak tomorrow.
>
> Thanks Tom
> --
> Ken Burton - N9KB
> 76 Palm Beach
> Hebron, Indiana
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>
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